We propose to analyze human polymorphic cell surface antigens not coded by the HLA supergene and to produce monoclonal antibodies against such structures using the technique of somatic cell fusion of a murine myeloma line with spleen cells from immunized mice. Alternative techniques of immunization are proposed. The monoclonal antibodies will be used to study the distribution of the alleles in the population, the distribution of the antigen in different tissues and to carry both formal and somatic cell genetic studies on the genetic control of these alloantigens. The reagents will also be used for the biochemical characterization and purification of the molecules carrying the antigenic determinants. The role of the characterized polymorphisms in tissue transplantation will be evaluated.